The present invention relates to data processing systems and more particularly to a system and method for providing an automatic back-up of a primary terminal associated with a cluster of secondary terminals in a point of sale system when the primary terminal is disabled from operation.
Retail sales transactions are brief exchanges between the operator and a point of sale (POS) terminal pertinent to a specific customer's purchases. The key values of a POS system are to provide timely information to the operators and to accumulate data pertaining to the sales transactions so that extensive reporting of the days of operation is possible at a later time. A typical food service POS system may consist of 2-15 POS terminals which are physically scattered around the retail establishment. These terminals must have simultaneous access to a "data base" which may contain pricing and other business information. Further, it is highly desirable that a failure of an individual terminal will not cause a total system failure or even loss of any significant data. Additionally, the number of POS terminals that are being operated during the day of operation may vary due to varying business conditions. Thus, in a fast food operation, the number of terminals that are required to handle lunch sales may be different from that required for either breakfast or dinner sales. Thus, the particular POS terminal that will be removed from the system during the day is not known beforehand.
Back-up systems found in the prior art have been limited to a designated back-up processor associated with the main processor for taking control of the data processing system when the main or primary processors is disabled. In order to prevent any disruptions of the processing operation, the back-up processor may receive the same data that the primary processor receives by listening to the communication channel over which the primary processor communicates with the secondary processors to detect the time that the primary processor is disabled so that the back-up processor can continue the communication without notifying the secondary processors that such an interruption has occurred. In U.S. Pat. No. 4,623,883, which is assigned to the assignee of the present invention, there is disclosed a communication switch which enables the the back-up processor to become the primary processor upon the switch detecting the disabling of the main or primary processor. In copending U.S. patent application No. 002,544, which is assigned to the the assignee of the present invention, there is disclosed a POS processing system in which the primary terminal supplies price look-up data to the secondary terminals in the system and in which a secondary terminal is designated as the back-up terminal to provide continuous data servicing to the secondary terminals when the primary terminal is disabled. Designating a terminal to be a primary or a back-up terminal requires that the designated terminal have a different hardware and software construction which adds to the complexity and cost of the system.